I have a situation similar to this one:

I have two datasets, this one:

from | to | frequency |
---|---|---|

a | a | 2 |

a | b | 3 |

and this one:

from | to | frequency |
---|---|---|

a | a | 3 |

a | b | 4 |

Now, I want to merge the two, keeping "from" and "to" variables the same, since they are exactly the same BUT, meanwhile, SUMMING the frequency.

This is what we should get:

from | to | frequency |
---|---|---|

a | a | 5 |

a | b | 7 |

### >Solution :

With base R we can use `aggregate`

+ `rbind`

```
> aggregate(frequency ~ ., rbind(df1, df2), sum)
from to frequency
1 a a 5
2 a b 7
```

Or, we can use `xtabs`

+ `as.data.frame`

+ `rbind`

```
> as.data.frame(xtabs(frequency ~ ., rbind(df1, df2)))
from to Freq
1 a a 5
2 a b 7
```

# Data

```
> dput(df1)
structure(list(from = c("a", "a"), to = c("a", "b"), frequency = 2:3), class = "data.frame", row.names = c(NA,
-2L))
> dput(df2)
structure(list(from = c("a", "a"), to = c("a", "b"), frequency = 3:4), class = "data.frame", row.names = c(NA,
-2L))
```